Many tactical shooters have adopted the .260 Remington as an alternative to the heavier-recoiling .308 Winchester. The .260 Rem has also performed well in the hands of long-range High Power shooters such as SSG Sherri Jo Gallagher, past National High Power Champion. The .260 Remington is basically the .308 Win necked down to .264 (6.5 mm) caliber. It can launch very high-BC 130-142 grain projectiles at impressive velocities. The ballistics of the .260 Rem allow it to shoot flatter, with less wind drift, than typical .308 Win loads.
For fans of the .260 Remington, very high-quality factory ammo is now available. ABM Ammo, a division of Berger Bullets just announced that it will produce two varieties of .260 Remington ammo.
ABM’s 260 Remington 140gr Berger Match Hybrid Target ammo is designed for class-leading ballistic and superior accuracy. Using the highest-BC 6.5 mm caliber bullet offered by Berger, the 140gr Hybrid, this load features less wind deflection and more energy on target than the competition. ABM claims that this Match Hybrid ammo is “unrivaled as a long-range 260 Remington factory ammo option.” Since it pushes a higher-BC bullet than other .260 Rem factory ammo, we’d have to agree with that statement.
Performance based on a 26″ barrel and sea level conditions.
Mission Ready .260 Rem OTM Tactical Load for Mag-Fed Rifles
ABM Ammo also offers .260 Rem factory ammo loaded with the NEW 130gr AR Hybrid bullet. The .260 Rem 130gr Berger Match AR Hybrid OTM Tactical load is optimized for the AR-10 platform or any magazine-fed rifle. Berger’s 130gr AR Hybrid bullet offers a 0.290 G7 BC. That’s very close to the 0.317 BC of the longer 140gr Hybrid. This, combined with a 2847 FPS muzzle velocity, provides excellent performance in a shorter COAL that feeds perfectly from box magazines.
In fact, if you run the ballistics (using JBM) using ABM’s published MVs, you’ll find that you give up nothing with the shorter bullet. At 600 yards, the 130gr “Mission Ready” load has 78.8″ (12.5 MOA) of drop. By comparison, the “Match Ready” load with 140-grainers has 80.3″ (12.8) MOA of drop at 600 Yards (That’s not a mistake — the smaller bullet has LESS drop because it has a higher MV to start.) At 1000 yards, the “Mission Ready” load is virtually identical to the “Match Ready” load: The 130gr ammo has 304.6″ (29.1 MOA) of drop at 1000 vs 303.4″ (29.0 MOA) for the 140gr ammo at the same distance. (These calculations are based on standard conditions at sea level, with ABM supplied MVs.)
Because the ballistics are so close, you may want to try both loads in your .260 Rem rifle, even if you single-load and are not restricted by mag length. Some barrels may have a preference for one bullet over the other.
Product Tip from EdLongRange. We welcome reader submissions.
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We know our readers are curious about the new Tipped MatchKings (TMKs) introduced by Sierra Bullets this year. Our friend Bill at Rifleshooter.com got hold of some of the .30-Cal 175-grain TMKs and tested them in his .308 Win rifle. He found the bullets were very consistent in weight. As for bearing surface, the SD was fairly low (.002″), but measurements varied from 0.400″ to 0.407″. Seven-thousandths variance is more than we like to see, as it may affect accuracy. Therefore we recommend you sort by bearing surface length before loading these in match rounds.
The new 175gr TMKs have a better BC* than the older-design 175gr BTHP MatchKings. The improved BC is a combination of a different shape and the plastic tip. Unfortunately, that tip increases the bullet’s overall length. Rifleshooter.com notes that this may be a factor those who are already loading SMKs to max mag length. With the new, longer TMKs you’ll need to put more bullet shank in the cartridge to maintain the same Cartridge OAL.
Bill explains: “The 175 TMK has an overall length of 1.380″, compared to 1.239″ of the SMK. The additional .141″ in length effects the OAL of the complete cartridge. In my .308 Winchester rifle, chambered with a Manson .308 Match reamer, the 175 TMK measured 2.950″ to the lands with the TMK, .070″ longer than 2.880″ capacity of a AICS magazine. While this isn’t a big deal for a shooter single loading his rifle, such as in F-Class … it is problematic with guns using a detachable magazine system.”
Measured weights of the Sierra 175gr TMK bullets were very consistent.
Bill tested for accuracy, but found the results somewhat disappointing, both with mag-length and single-shot-length loads. He believes more load development was in order. Keep in mind that Bill was NOT testing with a benchrest-grade rifle. On the plus side, Bill was pleased that he picked up some speed with the TMK: “Velocities were approximately 50 FPS faster than the 175 SMK with the same powder charge. This matches some reports I have read about the TMK being slightly faster than the SMK. However, my 175 SMK data was gathered during the winter when temperature were significantly cooler, I would not predict higher velocities with certainty.”
*Sierra advertises a G1 ballistic coefficient (BC) of .545 for speeds over 2400 FPS. This is an improvement over the 175 SMK, with an advertised G1 BC of .486 between 1800 and 2800 FPS and .505 over 2800 FPS. Bryan Litz of Applied Ballistics tested the 175 TMK and recorded a G7 BC of .267. That’s nearly 10% higher than the .243-value G7 BC of the 175gr SMK.
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In our Forum recently, there was a discussion about “improved” cartridges based on the .243 Winchester parent case. One popular such cartridge is the Super LR, a 30° long-necked wildcat. The 6mm Super LR was developed by Robert Whitley, who wanted something similar to the 6XC, but with “more boiler room” to push the 115-grain bullets comfortably at 2950-3050 fps.
To illustrate the Super LR for interested readers, we dug into our archives and found a report on a 6mm Super LR varmint rifle belonging to Barry O. (aka “TheBlueEyedBear”), a long-time AccurateShooter Forum member. A few years back, Barry put together an impressive 6mm Super LR long-range varminter on a BAT SV action. Barry actually sourced many of the components for this rifle through our AccurateShooter Forum Free Classifieds. CLICK HERE to read all about Barry’s Super LR BAT-Actioned varmint rifle, featured in our popular Gun of the Week Series.
CLICK Photo to Read Full Story
The Richard Franklin walnut LowRider stock (above) for Barry’s rifle came from fellow Forum member “Preacher”, who also did most of the metal work. The gun is chambered as a 6mm Super LR.
6mm Super LR Cartridge Design and Loading Advice by Robert Whitley, AR-X Enterprises
Conceptually, the 6mm Super LR is like a long-bodied 6XC (case body about .120″ longer). The Super LR has a long neck (.321″ vs. the .263″ long neck of the parent .243 Winchester case). The Super LR also has a 30° shoulder angle vs. the 20° shoulder angle of the .243 Winchester parent case. The Super LR has about 54 grains of H20 capacity, compared to 55 grains for the .243 Win and 49 grains H20 for the 6XC.
The Super LR has sufficient case capacity to shoot the 115gr 6mm bullets in the 2950 – 3000 fps range without being “on the edge” of maximum pressure. If you do not need to run sustained fire in long strings, you can “hot rod” things more. Testing has shown that the Super LR can run the 115s up around 3100 fps without issues. With the 105-108 grain 6mm bullets, the 6mm Super LR can push them up in the 3150-3200 fps range with the right powders. In addition, if you like to shoot the 105-108 grain bullets close to the lands, or engaging the lands, the Super LR cartridge case neck is long enough to give most of them a good bearing surface purchase, even if the chamber is throated for the 115gr bullets. That gives the 6mm Super LR cartridge great versatility.
The 30° shoulder angle of the 6mm Super LR is another good feature of the Super LR. Not only does it help to avoid the throat-torching effect that people associate with the .243 Winchester (because of the .243’s short neck and 20° shoulder angle), but the 30° shoulder angle has also been a hallmark of some very accurate cartridges such as the 6 PPC, 6mm BR, 6XC, and 6.5 x 47, to name a few.
The 6mm Super LR wildcat is easy to make. Robert Whitley figured out how to reform domestic .243 Win brass with one simple pass through a Redding 6mm Super LR full-length sizing die. Robert has commissioned these dies from Redding. Call Robert at (215) 348-8789 to order.Learn more about the 6mm Super LR on Whitley’s www.6mmAR.com website.
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Photo shows Bryan Litz (on right) and tester Mitchell Fitzpatrick. Bryan said: “Only 2,445 rounds to go! We’re testing over 50 ammo types in five different twist barrels… science can be exhausting!”
Do you know the actual BC (Ballistic Coefficient) of your rimfire ammunition? Well Applied Ballisitics will soon have answers for you. Bryan Litz and his team of testers have been working on a Herculean project. They’ve been testing over fifty types of .22 LR ammo, using five different twist-rate barrels.
Western Powders (which sells Accurate, Ramshot, and Norma powders) has published an article on case inspection and preparation. There are many tips in this article that can be useful to precision hand-loaders. For example, every time you open a new box of cartridge brass (particularly from domestic makers), you should inspect each case for flaws.
TIP ONE: Visual Inspection — Finding Flaws
Cases are mass-produced items and malformed ones are relatively common. Inspect each case carefully looking for obvious defects. A bench-mounted magnifying glass with light is a real help for the over-40 crowd. The main defects will be cracks in the neck or case body, crushed shoulders or deep creases in the neck. Next check the primer pocket. It is also fairly common to find flash holes that are damaged or, more rarely, not concentric to the primer pocket.
Imperfections like small dings in the case body, or necks that are not completely symmetrical do not have to be eliminated at this step. Damage of this sort is usually from loose packaging and usually has not seriously damaged the brass. [Running an expander mandrel in the neck] and fire-forming will iron out these largely cosmetic issues.
ABM Ammo, a division of Berger Bullets, has introduced new, high performance .308 Winchester factory ammunition, loaded with the high-BC, 185gr Berger Juggernauts. The long-loaded “Match Ready” version of this ammo is designed for Palma (Full-bore) and F-TR shooters. A “Mission Ready” version, loaded shorter to mag length, is designed for tactical and military applications. These two new offerings should “raise the bar” for long-range performance with factory .308 Win ammo.
Offering a high Ballistic Coefficient (0.560 G1, 0.283 G7), the 185-grain .308-caliber Juggernaut bullet is designed to remain stable even in the transonic zone. This way it offers good performance at extended distances, contributing to higher hit percentages at longer ranges.
AccurateShooter.com has released the most complete discussion of the 6.5×47 Lapua cartridge ever published. Our new 6.5×47 Cartridge Guide is packed with information. If you own a 6.5×47 rifle, or are thinking of building a rifle with this chambering, definitely read this Cartridge Guide from start to finish. Our comprehensive, 5000-word article was researched and written by the 6.5 Guys, Ed Mobley and Steve Lawrence. Both Ed and Steve shoot the 6.5×47 Lapua in competition and they are experts on this accurate and efficient mid-sized cartridge.
You’ll find everything you need to know about the 6.5×47 Lapua in our new Cartridge Guide. We cover ballistics, reloading, die selection, and we provide an extensive list of recommended loads, for bullets from 120 to 140 grains. You can read interviews with respected experts who’ve built and tested many 6.5×47 rifles. The Guide includes helpful tech tips such as how to maximize the powder fill in your cases. This Cartridge Guide can put you on the “fast track” — helping you develop accurate, reliable loads with minimal development time.
6.5×47 Lapua Cartridge Guide Highlights:
Comprehensive Load Data
Best Bullets and Primers for 6.5×47
Ballistics Comparison Charts
Sizing and Seating Die Options
6mm-6.5×47 (Necked-Down) Options
Ask the Experts Section
Tips for Accurate Reloading
Brass Life and Annealing
Chambering and Gunsmithing Tips
6.5×47 Lapua for Hunting
6.5×47 Lapua for Tactical Competition
6.5×47 Factory-Loaded Ammo
Here is a sample from the 6.5×47 Cartridge Guide’s Ask the Experts Section. This is an interview with Rich Emmons, one of the founders of the Precision Rifle Series:
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The .260 Remington and the 6.5×55 Swedish (aka 6,5x55mm SE) are both very popular cartridges with hunters and target shooters. The 6.5×55 has a long military heritage and a great record as a hunting round. The .260 Rem, essentially a .308 Win necked down to .264 caliber, is a more recent cartridge, but it grows in popularity every year, being one of the top cartridges for tactical/practical competitions. It offers better ballistics and less recoil than the parent .308 Win cartridge. In our Shooter’s Forum, respected UK gun writer Laurie Holland provided a good summary of the differences between the two chamberings. Laurie writes:
The 6.5×55 case has 6 or 7% more capacity than the .260s, even more in practice when both are loaded to standard COALs with heavy bullets, which sees them having to seated very deep in the .260 Rem using up quite a lot of powder capacity. So loaded up for reasonable pressures in modern actions, the 6.5×55 will give a bit more performance.
The issue for many is what action length is available or wanted, the 6.5×55 requiring a long action. So sniper rifle / tactical rifle competitors will go for the .260 Rem with the option of the many good short-bolt-throw designs around with detachable box magazines (DBMs). If a bit more performance is needed, the .260 AI (photo right) can yield another 100-150 fps velocity, depending on bullet weight.
Berger Twist-Rate Stability Calculator
On the updated Berger Bullets website you’ll find a handy Twist-Rate Stability Calculator that predicts your gyroscopic stability factor (SG) based on mulitiple variables: velocity, bullet length, bullet weight, barrel twist rate, ambient temperature, and altitude. This very cool tool tells you if your chosen bullet will really stabilize in your barrel.
LIVE DEMO BELOW — Just enter values in the data boxes and click “Calculate SG”.
Berger Bullets has just announced a new 6.5 mm (.264 caliber) 130gr Hybrid projectile. Optimized for magazine-length seating (and AR10-friendly), the new 130gr bullets should be ideal for tactical comps and the PRS series. We expect this new bullet to work great when loaded in modern mid-size cartridges such as the 6.5×47 Lapua and 6.5 Creedmoor. Berger’s new 6.5mm 130gr Match AR Hybrid OTM Tactical bullet (could Berger come up with a longer name?) will soon be released to the public. Berger says this new 130-grainer is the first of many new bullet designs to be introduced in the next few years. Here is a run-down on the new bullet from its designer, Bryan Litz of Applied Ballistics.
NEW 130gr Hybrid — Behind the Design
by Bryan Litz, Berger Chief Ballistician
Intelligent bullet design and selection begins with an understanding of application constraints. For bullets that will be used in unlimited rifles, there are few constraints and performance can truly be maximized. However, many shooting applications have realistic constraints such as magazine feeding of loaded rounds. In constrained applications, you need to ask the question: “What’s the best bullet that will work within the constraints of my shooting application?”
The new Berger 6.5mm 130 grain AR Hybrid OTM Tactical bullet is specifically optimized for maximum performance in magazine-length ammo.
6.5mm cartridges are the second most common cartridges used by top shooters in many of the Precision Rifle Series (PRS) matches, with 6mm being the most common. These kinds of tactical matches all have stages that require repeating rifles — either AR-10 platforms or bolt guns — so magazine feeding is a must. Recognizing that Berger did not have an option that was truly optimized for this particular application, we went to work and the latest 6.5mm Hybrid is the result.
The new Berger 6.5mm 130 grain AR Hybrid OTM Tactical bullet is specifically optimized for use in loaded ammo with COAL constraints for magazine feeding. This bullet maximizes overall performance through BC as well as achievable muzzle velocity in mid-capacity 6.5mm cartridges fed from AR-length magazines.
What makes this bullet optimal for magazine length ammo? To start with, the nose of the bullet is constrained in length so that when it’s loaded to mag length in 6.5mm cartridges such as the 6.5mm Creedmoor, 260 Remington and 6.5×47 Lapua, the nose of the bullet won’t be pushed below the case mouth. This can be an issue with some of the heavier 6.5mm bullets like the 140s. Furthermore, the hybrid ogive design is not sensitive to jump distance like some other designs such as the VLD.
Another consideration of length-constrained ammo is how much of the bullet is pushed down into the case. The inside of the case is for powder, and the more space you take up with bullet, the less powder you can fit in. Less powder means less total energy available, and muzzle velocity is depressed. A bullet weight of 130 grains is an optimal balance between external ballistic performance (BC) and internal case capacity considerations which translate into muzzle velocity. Further to this objective, the AR Hybrid has a minimal air gap in the front of the nose, which allows the bullet to have an even shorter OAL. When dealing with length-constrained designs, you need to pack as much bullet into as little length as possible< to optimize overall performance. Another advantage of making the bullet shorter is that stability, including transonic stability, is improved.
Although this design is length-constrained, the combination of a hybrid ogive and 7 degree Boat Tail produce a very respectable G7 form factor of 0.920 which is within 1% of the popular 6mm 105 grain Hybrid. See below for full live fire ballistic performance data.
The 6.5mm 130 grain AR Hybrid will be barely stable from a 1:9″ twist, and reaches full stability from a 1:8″ twist which is common for many 6.5mm rifles. Visit the Berger Bullets twist rate calculator to get more detailed stability information on your specific barrel twist, muzzle velocity and environment.
Cartridge Selection for Magazine Length Constraint — Advanced Analysis
The trend to smaller calibers in magazine-fed rifles is happening for a very good reason. For a .308 Winchester round, you only have 2.37 calibers of nose length available for the bullet to protrude from the case. Such a short nose will have relatively high drag for the caliber. By contrast, smaller calibers such as 6.5mm and 6mm have proportionally more length available for the nose to protrude from the case and still fit in the same COAL constraint. Proportionally longer noses mean lower drag. Proportionally longer bullets mean higher sectional density. Combine an elevated sectional density with lower drag, and you get higher BC bullets. For example, consider a 175 grain .30 caliber bullet commonly used in .308 Winchester M118LR-type ammo. These 175 grain bullets have G7 BCs in the neighborhood of .243 to .260. Neck the .308 down to 6.5mm (260 Remington) or 6mm (.243 Winchester) and now look at the BCs of the bullets available in these calibers which work within the same magazine length constraint. The 6.5mm 130 grain AR Hybrid has a G7 BC of 0.290, and the 6mm 105 grain Hybrid has a G7 BC of 0.278 — both of which are higher than the .30 cal 175 grain bullet BC. Furthermore, you get hundreds of feet per second more velocity with the necked-down cartridges as well.
All of the above translates into higher hit percentage. See the caliber comparison chart below* which is an excerpt taken from the book: Modern Advancements in Long Range Shooting which addresses this and many other topics in even more detail.
*The Weapon Employment Zone (WEZ) analysis shown above is for a 1000-yard shot on a standard IPSC silhouette in an uncertain environment having: +/- 2 mph wind, +/- 1 yard range, Muzzle Velocity SD of 10 fps, and a rifle shooting 1 MOA groups.
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In our Shooters’ Forum, a member recently noted that he needed to pull down (disassemble) some ammunition that was loaded incorrectly by one of his shooting buddies. You can use an impact puller to do this task, but if you have more than a dozen rounds or so, you may prefer to use a collet-style bullet puller. These work very quickly and positively, making quick work of big jobs. The efficiency of the collet-style puller is worth the investment if you frequently disassemble ammo. These devices retail for under $25.00 (collets sold separately). Normally, you’ll need a specific collet for each bullet diameter. But collets are not that costly, so this isn’t a big deal, particularly if you only load a few calibers, such as .223, 6mm, and .308.
Hornady and RCBS use different mechanisms to tighten the collet around the bullet. On Hornady’s Cam-Lock Bullet Puller, a lever-arm on the top of the bullet puller serves to tighten the collet around the bullet. Simply rotate the lever from the vertical to the horizontal position to grab the bullet. Lower the ram to remove the case. The bullet will drop out when you return the lever arm to the vertical position. This is demonstrated in the video below:
We are sad to report that long-time Forum member Frank S. (aka fdShuster) passed away this year. Frank was a very knowledgeable shooter who was always willing to help others. Here is one of Frank’s smart inventions. He devised a way to measure the length of a rifle’s chamber using a fired cartridge case. Frank’s system works by cutting a “collar” from part of the case neck. This then slips over a bullet seated in a case loaded without powder or primer. As you chamber the dummy round, the collar will move back to indicate the full length of the chamber. (Make sure the bullet is seated well off the lands so the dummy round can chamber fully.)
Varmint hunters rejoice. At long last Hornady-brand 17 WSM (Winchester Super Magnum Rimfire) ammo is available. In case you haven’t heard by now, the 17 WSM is the fastest rimfire cartridge ever created. With muzzle velocities in the 3000 fps range, the 17 WSM enjoys a considerable advantage over even the hottest 17 HMR rounds you can buy. Winchester has produced its own 17 WSM ammo, but that was hard to find. Now Hornady is producing 17 WSM ammo loaded with 20gr V-Max tipped bullets. Grafs.com has the new Hornady ammo in-stock now at $15.99 per box of 50 rounds. Order soon if you want some. We expect this stuff to go very quickly…
What’s the next best thing to a stockpile of gleaming, freshly-loaded ammo? How about a movie showing gleaming, freshly-loaded ammo being made — from start to finish? The five-minute video below shows the ammunition production process at the Lake City Army Ammunition Plant, a division of ATK. Lake City is the largest producer of small arms ammunition for the U.S. military, producing roughly four MILLION small-caliber rounds every day.
This promotional video does go a bit overboard at times in a self-congratulatory sense. But the video is definitely worth watching — it is fascinating to watch the process of creating cartridges — from the drawing (or extrusion) of raw brass into casings to the placement of projectiles and primers.
Quick History of Lake City Ammunition Plant Lake City Army Ammunition Plant (LCAAP) is a 3,935-acre government-owned, contractor-operated facility in Independence, Missouri that was established by Remington Arms in 1941 to manufacture and test small caliber ammunition for the U.S. Army. The facility has remained in continuous operation except for one 5-year period following World War II. As of July 2007, the plant produced nearly 1.4 billion rounds of ammunition per year. Remington Arms operated the plant from its inception until 1985, when operations were taken over by Olin Corporation. From April 2001 through the present, it has been operated by Alliant Techsystems (ATK), which in February 2015 split into two separate companies, Orbital ATK and Vista Outdoors.
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Our friend Darrell Buell has a new Beast — a monster 64-inch-long .375 CheyTac that weighs more than 70 pounds! Designed for ultra-long-range shooting (two miles and beyond), this beast represents the state-of-the-art in extreme long-range rifles.
Darrell reports: “This rifle is pretty much purpose-built to shoot 2+ miles extremely accurately. It is a .375 CheyTac (lengthened) built on a BAT 2.5″ action. The custom 35″, 1:10″-twist Brux barrel is a fat, 2″-diameter ‘straight taper’ with fluting. A custom 5″-long muzzle brake is fitted at the end. All barreled action work was done by R.W. Snyder Custom Rifles. The stock was created to fit the build by PDC Custom, and the massive muzzle brake as well.” The “bridge” at the end may look like a barrel block, but it’s not — the barrel completely free-floats. (The Picatinny rail on top of the bridge allows use of an overhanging bipod as an alternative to the JoyPod).
Darrell has lots of elevation on tap: “With 150 MOA in the Ivey rings, another 20 MOA in the scope rail, 55 MOA in the Nightforce Competition scope, and 10 MOA in the FCR-1 reticle, there’s an impressive +235 MOA available.”
Based on the questions we get on a daily basis on our 800 (Customer Support) line, twist is one of the most misunderstood subjects in the gun field. So let’s look deeper into this mystery and get a better understanding of what twist really means.
When you see the term 1:14″ (1-14) or 1:9″ twist, just exactly what does this mean? A rifle having a 1:14″ twist means the bullet will rotate one complete revolution every fourteen inches of the barrel. Naturally a 1:9″ turns one time every nine inches that it travels down the barrel. Now, here’s something that some people have trouble with. I’ve had calls from shooters thinking that a 1:14″ twist was faster than a 1:9″ because the number was higher with the 1:14″. The easiest way to remember this is the higher the number, the slower the twist rate is.
If you wonder how ammo is made, starting with raw metal, check out this video from Hornady. It shows how bullet jackets are formed from copper, followed by insertion of a lead core. The jacket is then closed up over the core with the bullet taking its final shape in a die (a cannelure is applied on some bullet types). Next the video shows how cartridge brass is formed, starting with small cups of brass. The last part of the video shows how cases are primed and filled with powder, and how bullets are seated into the cases, using an automated process on a giant assembly-line. CLICK Link below to watch video:
If you look at that 5-round group you might think it was shot with a 6 PPC or maybe a 6mmBR. But no, this was done with heavy 180gr Berger Hybrid bullets and the .284 Shehane, an improved version of the .284 Winchester. In fact, this impressive sub-quarter MOA group was shot while fire-forming with a very well-worn barrel!
Here’s a 5-shot 0.191″ group at 100 yards with my .284 Shehane fireforming loads. This barrel has 2200 rounds through it. It had 2000 as a straight .284 Win and then I set it back to .284 Shehane to form brass with. This was the first five rounds through it after I cleaned it after the last match. [The load was] 180 Hybrids with 54.0 grains of H4831 SC.
Ya, I figured why not I had some old barrels laying around so I just chopped 2″ off the back and 1″ off the front and chambered it up as a Shehane. Had 1000 pieces to fireform and didn’t want to do all that on a brand new barrel.
My fireform loads are going 2765 FPS. I have a 29″ barrel also though since it’s a setback. Once you get it formed I would push it faster than that or I wouldn’t even bother with the Shehane. My old straight .284 load at 2890 fps had ES spread in single digits for 10 shots. I figured if I get it up to 2935-2950 fps that will be a point or two saved in a several day match.
Fellow .284 Shehane shooter Erik Cortina notes that the .284 Shehane has a velocity edge over the straight .284 Win because it holds more powder: “The Shehane has more capacity than the .284 Winchester. Ryan is using 54.0 grains simply as a fire-forming load. Typical load for a Shehane is around 57.0 grains of Hodgdon H4831 SC.” By blowing the sidewalls out 0.010″, the .284 Shehane picks up about 3.3 grains of extra case capacity. That enhancement makes a BIG difference. The extra boiler room is enough to drive the 180s at 2900-2950 fps with H4831sc, with long barrels.
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“The overturning moment MW tends to rotate the bullet about an axis, which goes through the CG (center of gravity) and which is perpendicular to the plane of drag….
Ruprecht Nennstiel, a forensic ballistics expert from Wiesbaden, Germany, has authored a great resource about bullet behavior in flight. Nennstiel’s comprehensive article, How Do Bullets Fly, explains all the forces which affect bullet flight including gravity, wind, gyroscopic effects, aerodynamic drag, and lift. Nennstiel even explains the rather arcane Magnus Force and Coriolis Effect which come into play at long ranges. Nennstiel’s remarkable resource contains many useful illustrations plus new experimental observations of bullets fired from small arms, both at short and at long ranges.
Shadowgraph of .308 Winchester Bullet
A convenient index is provided so you can study each particular force in sequence. Writing with clear, precise prose, Nennstiel explains each key factor that affects external ballistics. For starters, we all know that bullets spin when launched from a rifled barrel. But Nennstiel explains in greater detail how this spinning creates gyroscopic stability:
Sierra Bullets recently profiled Mike Walker, Remington engineer and first president of the National Benchrest Shooters Association (NBRSA). In the vintage photo above, Mike is shown with his Remington-actioned benchrest rifle at the 1994 Super Shoot. Mike had reason to smile — at that 1994 event, Walker set a 100-yard small group record with a phenomenal .046″ five-shot group. Mike was truly one of the “founding fathers” of modern benchrest shooting. As Sierra notes: “The field of rifle accuracy and the sport of benchrest shooting would be very different today, were it not for this man.”
Along with Remington Engineer Jim Stekl, Mike Walker helped develop a wildcat that became the 6mmBR cartridge. The original 6mm Benchrest Remington wildcat was a necked-down .308 x 1.5″ Barnes cartridge. That Barnes cartridge was derived from the .308 Winchester case, as shortened to 1.5 inches. The parent .308 Win case has a large primer pocket (though Remington did make a special run of small primer pocket .308 brass). Remington later made factory small primer pocket 6mm BR Rem brass. Compared to the original 6mm BR Remington case, the modern 6mmBR Norma cartridge has very slightly different dimensions, with a small primer pocket and a small 1.5mm (0.059″) flash-hole.